Electric wave signaling system



April 19, 1932.

G. C. DE COUTOULY ELECTRIC WAVE SIGNALING SYSTEM Filed July 6, 5

2 Sheets-Sheet lm/emor day/aye 6. defied/004 G. C. DE COUTOULY ELECTRIC WAVE SIGNALING SYSTEM April 19, 1932.

Filed July 6. 1925 2 Sheets-Sheet 2 day/ave 6' defowaul 5/ 1477 Patented Apr. 19, 1932 eus'ravn cnAaLr-s DE CO'UTOULY, or ci-ra rnaiu, JERSEY, ASSIGNOR T0 wnsrri nn' HQE ELECTEIGCOMPANY, INCOBFGRATED, OF NEW YORK, N. Y., A CORPORATION OF NEW YORK ELECTRIC WAVE SIGNALING SYSTEM Application filed July 6,

This invention relates to electric wave signaling systems and in particular to high frequency elegraph transmitting systems.

In the operation of high frequency transmitters, and especially high power radio transmitters, numerous problems are encountered and must be solved in order to secure reasonably continuous and successful operation. Among these problems is the important one involving frequency control. Anot is the prevention of undesired teedbacl: of energy from the output circuit of the transmitter to its input circuit, which may cause the generation of parasitic oscillations and serious interference with signals. Still another problem arises in connection with the provision oi power supply sources of suitable character for supplying the space discharge tubes.

When it is desired to transmit signals at high power, it is ordinarily necessary to provide a considerable number of tandem connected sta es of amplification. This is in part necessa y, because, as usually operated,

g; the amplifying power of each stage islimited by virtue of the fact that if too great amplification is attempted 111 any one stage the liabilit or" producing parasitic oscillations ,1 1 t in the system is increased. Such oscillations V are detrimental because, among other things,

they cause the transmission of waves of a difrerent length than has been assigned to the particular station and hence, not only cause interference with other signaling channels or systems, but also make easier the unauthorized reception of slgnals.

It is an. object 01" this invention to control large amplitude oscillations in accordance 1925. Serial No. 41,494.

duction and frequency of oscillations generated at another point. I

A still further object is to control the feed back of energy between output and input circuits of a space discharge amplifier by compensating to a desired degree the inherent capacity of the amplifier.

A further object is to transmit signals at high power by producing oscillations in a plurality of amplifying stages controlled as to frequency by oscillations from a source of small power.

A feature of the invention is a piezo=electric crystal controlled oscillator, adapted to control the frequency of oscillations generated in a series of power amplifiers.

Another feature is a radio transmitter, comprising a plurality of regenerative space discharge amplifiers in tandem, each adjusted to the verge of oscillation and arranged to be controlled, as to the establishment-of oscillations, in accordance with signals.

A further feature relates to tuned coupling circuits for regenerative space discharge am plifiers in tandem, and to means for compenpower together with increased selectivity and stability are secured.

An additional feature relates to a space discharge amplifier circuit comprising a condenser for compensating the inherent capacity between electrodes of the amplifier, which condenser may be varied to adjust the amplifier circuit so that it is on the verge of pro ducing oscillations.

Another feature is a coupling circuit, arranged in common to an antenna and an amplifier, which is adapted to function as a filter to selectively transmit desiredwav'es, while greatly attenuating and impeding undesired waves.

An additional feature relates to the sources of power for space discharge tubes and involves the provision of sources adapted to supply currents at a plurality of different potentials to the space discharge tubes of a radio transmitter, including tubes each of which is adapted to generate oscillations and requires a different amount of power from the others.

Cit;

The invention involves, in its broader aspects, a source of oscillations of low power and of very constant frequency, for example, a vacuum tube oscillation generator controlled by a piezo crystal. The source of oscillations is coupled to an amplifier system comprising a plurality of stages. The amplifier may comprise vacuum tubes and associated circuits in tandem. each being adjusted to the verge of instability and capable of being set into an oscillatory condition by the feeble oscillations from the controlling source. The frequency of the oscillations produced by the amplifier may also be controlled by the frequency of the first source.

The space discharge tubes of the system are preferably coupled by resonant coupling circuits having means such as balancing condensers, arranged in some manner such as is described in U. S. Patent No. 1,784,957 to P.

H. Betts, June 30, 1930, for compensating the inter-electrode capacity of the tubes to prevent the production of parasitic oscillatio For signaling purposes. the amplifiers may be controlled by a telegraph key adapted to stop or start the oscillations. A source of audible frequency waves is further provided and. may be arranced to modulate the generated oscillations. This source may be controlled by a signaling device. such as a telegraph key. The former method is known as continuous wave (0. V7.) signaling and the latter known as modulated continuous wave signaling.

Proper shieldin for the separate tubes and for the piezo-control element is provided to insure greater constancy of frequency, to prevent interference from external sources, and to avoid the interchange of energy between the stages included in the system. which would tend to produce other undesired oscillations.

The sources of power for the space discharge tubes may be direct or alternating current generators, either with or without suitable current rectifiers.

' pled to a. power amplifier including the stages 20 and 30. The output circuit of stage 30 is coupled by a unit 35 to an antenna 65. The respective units 10, 20, 30 and 35 as well as the filter 616263 are each included in a shielding compartment which completely encloses it except for suitable openings through which certain conductors pass. The shielding is shown by the broken lines 50. The oscillator includes a space discharge tube 11 having a control electrode, cathode and anode. The

input circuit for this oscillator, which is connected to the control electrode and cathode includes, in series, the high frequency choke coil 12, and resistance 13. The filament of tube 26 is connected in series with the filament of tube 11. The space current circuit for tube 11, connected to its anode and cathode, includes the high frequency choke coil 14: in series with direct current generator 15 and the filament of tube 26. shunted by a condenser 16 which serves to eliminate commutator ripples from the space current. A feed-back circuit for the tube 11 includes a blocking condenser 17 ha *ing one terminal connected to the anode, a resonant circuit 18, 22. a second blocking condenser 24 and a piezo electric device in series therewith, the latter having its remote terminal connected to the control. electrode.

Element 18 of the resonant circuit is an adjustable inductance, and element 22 is an adjustable condenser. This circuitis preferably adjusted to the frequency at which oscillations are to be generated. Piezoelectric element 25, wh'ch cooperates with resonant circuit 18, 22 in determining the frequency of oscillations, may be constructed in any well known manner and consist of a quartz crystal of desired shape positioned between conductive plates. The manner of cutting and mounting such crystals is described in applications of W A. Harrison, Serial No. 734.189, filed August 2-6, 1924 and Serial No. 7 30.165. filed August 5, 192 1.

The high frequency output circuit for the oscillator 10 includes the condenser 17 reso nant circuit 18, 22 lead 19 and condenser 20". The remote terminal of condenser 20 is connected to the shield conductor 50 which in turn is connected by a condenser 21 to the filament of tube 11. Condensers 17, 20 and 21 are designed to provide low impedance to high frequency waves.

The amplifier stage 20 includes a power space discharge tube 26 having an input circuit connected to its control electrode and cathode, which be traced from the control electrode through resonant circuit 18, 22 lead 19. switch 28, resistance 29, choke coil 30', resistance 31 to ground and from this point as already traced to the cathode of tube 26. By throwing switch 28 from contact 28 to contact 28 tone generator 27 may be included in the c rcuit traced. A space current circuit for tube 26 is connected to its anode and cathode and includes high fre quency choke coil 32 in series with low frequency choke coil 33. direct current generator 34:, resistance 29, choke coil 30 and resistance 31. The circuit just traced fro n the point intermediate the choke coils 32 and 33 to ground is shunted by a resistance 35 and condenser 36 in parallel. Condenser 36 in cooperation with cholte coil 33 provides a filter for eliminating commutation ripples from he generator 15 is tor 67.

the current supplied to the space path of tube 26. Tube26 likewise has a feed-back circuit including, in series, condenser 37, resonant circuit 38, 40, and adjustable condenser 42 connected between its anode and control. electrode. Resonant circuit 38, 40 is likewise tuned to the frequency of oscillations which it is desired to generate.

A T arrangement of adjustable resistances 44, 44 and 44 is included between the output circuit of tube 26 and the input circuit of tube 43 in the amplifier stage 30. By means of these resistances, the voltage of waves supplied to the tube 43 may be adjusted to the desired value and at the same time, the impedance of the circuit may be matched to the respective output and input impedances of tubes 26 and 43. A blocking condenser 45 is included between resistance 44 and the control electrode of tube 43.

A suitable average potential is supplied to the control electrode of tube 43 by a generator 47 which is connected thereto by a path including a series high frequency choke coil 46. The generator 47 is shunted by a condenser 48 for ripple suppression and a bypass condenser 49 is provided to supply a low impedance path for high frequency waves to ground. Space current is supplied to tube 43 by a rectifier 54 connected to an alternating current source 55. The rect fier is provided with a filter having an inductance 52 and a condenser 53 and is connected to the anode in series with a high frequency choke coil 51. A high frequency output circuit for tube 43 is connected to the anode and cathode and includes a condenser 56 in series with resonant circu t 57, 58, and a low pass filter 61, 62, 63 to ground at the shield conductor 50. The antenna 65 is also connected to ground by a path including adiustable inductance 64 and a variable condenser 63 in series. Condenser 63 is common to the output circuit of tube 43 and to the antenna circuit. The filter 61, 62,

l 63 is designed to transmit a band of frequencies including the fundamental of the generated oscillations and to constitute a capacity reactance at the frequency of transmitted waves, and to correspond to the proper coupling capacity to be inserted between the out put and antenna circuits. For harmonic frequencies the filter constitutes a high impedance path for excluding these frequencies from the antenna circuit.

A feedback path for tube 43 connectedbetween its anode and control electrode'ineludes condenser 56, a small portion of inductance 57, adjustable condenser 59, resonant circuit 38, 4O resistances 44 and. 44 and condenser 45.

The filaments of tubes 11 and 26 are arranged in a series circuit including adjustable resistance 66 and direct current genera- Thefiliament of tube 43 is connected key 70 to prevent arcing at the contacts.

Choke coil 69 in series with key 70, and choke coil 30" in series with resistance 31 cooperate to reduce the number of harmonic compo nents produced upon interrupting the circuit by key 70 during signaling which produce so called key clicks.

In the operation of this system, oscillations are produced in the generator 10 by virtue of the feed-back coupling between the input and output circuits of tube 11. Since this feed-back circuit includes the piezo-electric device 25, the frequency of oscillations is the.

termined by a natural frequency of the piezo crystal in the manner set forth in the application of W. A. Marrison, Serial No. 730,165, filed August 5, 1924.

The amplifiers 20 and 30 are normally adjusted by means of condensers 42 and 9 to be in a condition upon the verge of instability L such that when energy is supplied from the low power oscillator to the input circuit of tube 26, oscillations are established in the amplifier and when waves of the frequency of these oscillations are transmitted to the input circuit of tube 43, similar oscillations are established in its circuit. The tubes 26 and 43 and associated circuits are so designed and adjusted that the frequency of the oscillations generated therein is controlled in accordance with the frequency of oscillations in the generator 10. The control of the oscillations in amplifiers 20 and 30 by thewaves from piezo oscillator 10 results from the tendency of two waves closely related as to frequency to pull into step or into synchronism when combined. Since the piezo crystal maintains the frequency of waves produced by generator 10 substantially constant, it follows that the oscillations generated in amplifiers 20 and 30, will fall into step with these waves and hence will likewise be held substantially constant as to frequency.

The present invention is of great advantage because by regeneration a much greater amplification of energy may be secured than by the ordinary use of amplifier circuits. Again the present arrangement for controlling the frequency allows this method of amplification to be successfully used. The number of space discharge tubes required for a given amplification is accordingly reduced.

Amplifier 20 is designed to handle a considerably larger amount of power than oscillator 10 and amplifier is designed to ban-- dle considerably more power than amplifier 20. In practice the space discharge tube as would ordinarily be a water-cooled tube designed to handle power up to kilowatts. Tube 26 may be designed to handle power up to 250 watts and tube 11 may be designed to handle power up to approximately 5 watts.

The oscillations produced in power amplifier 30 are transmitted through resonant circuit 57, 58 and through filter 61, 62, 63 to the antenna 65. The antenna circuit is prefer ably tuned by means of adjustable inductance 64 or condenser 63 or both to the frequency of the waves to be transmitted.

Signaling is accomplished by starting and stopping the oscillations in generators and under the control of key 70. The control electrode of tube 26 normally has a potential impressed upon it which is suflicient to block or at least reduce the flow of space current through itto such value that oscillations are not generated. When oscillations are stopped in tube 26 they are also stopped in tube 43 which has its circuits normally adjusted a little below the oscillatory condition as already explained. The polarizing potential for tube 26 is obtained by the drop in potential across resistance 29, choke coil 80 and resistance 31. These elements are common to the input and output circuits of tube 26 and hence they are traversec by the space current to'the tubes. 1 esistance is pro vided to maintain a flow of current through the elements 29, 80 and 31 even when tube 26 has substantially no space current fiowin therein thus preventing any change in the polarizing potential when the space current changes. lVhen key is closed, resistance 31 is substantially short-circuited and the potential applied to the control electrode of tube 26 is'so reduced that oscillations are established in the amplifier. These oscillations produce similar oscillations in amplifier 30 and waves of corresponding frequency are radiated from antenna 65. When key T0 is opened, the blocking potential is again applied to tube 26 and the oscillations in amplifiers 20 and 30 are stopped. This method of signaling constitutes continuous wave signaling.

If it is desired to signal by the modulated continuous wave method switch 28 should be moved from contact 28 to contact 28". Generator 27 is thereby included in series in the input circuit of tube 26. The oscillations generated by amplifiers 20 and 30 are accordingly modulated in accordance with waves from generator 27 which are preferably within the audible range. Key 70 con- 'trols the production of oscillations in ampli fiers 20 and 80 in the same manner as before so that high frequency oscillations modulated in accordance with low frequency waves are supplied to the antenna 65 under control of 65 key 70,

In Fig. 2, a circuit, operating on the same general principle as that shown in Fig. 1, is illustrated. This circuit includes a low power piezo crystal controlled oscillator 10, a regenerative amplifier 20 and a second regenerative amplifier 30. The latter is coupled by a suitable capacity 63 to antenna 65.

An additional amplifier 10 not included in the circuit of Fig. 1 is interposed between the control oscillator 10 and the power amplifier 20 for the purpose of preventing reaction of the amplifier 20 upon the control oscillator 10. The oscillator 10 includes the tube 11 having an input circuit connected to its control electrode and cathode including the high frequency choke coil 12 and the resistance 29 which has its remote terminal connected to ground and thence to the cathode of tube 11 by a path including shield conductor 50 and condensers in shunt to the secondary winding of transformer 76, which is connected to the filament of tube 11. The feed-back circuit of tube 11 is substantially identical with the corresponding circuit described in connection with amplifier 10 of Fig. 1 and includes the piezo crystal control element 25 included in a separate shielding compartment 25. A mid-tap on inductance 18 of resonant circuit 18, 22 is connected by the lead 19 directly to the shield conductor 50.

The additional amplifier 10 comprises the space discharge tube 77 having its control electrode connected directly to the control electrode of tube 11 by a path including the resistance 78. This resistance reduces the coupling between the grids of tubes 11 and 77 and increases the negative grid voltage applied to tube 77 over that supplied to tube 11. The anode of tube 77 is connected in parallel to the anode circuit of tube 11 by a path including the high frequency choke coil 14. The space current paths for tubes 11 and 77 may be traced through the respective choke coils 1 1 and 14: to the positive brush 98 of a double armature direct current generator 79 through the armature taps 81, slip rings 82 and associated brushes, through the star connected coils 83 to ground and from ground to the cathodes of tubes 11 and 77 which are connected in parallel to the secondary winding of transformer 76.

A high frequency output circuit for tube 7'? is connected to its anode and cathode and includes condenser 84: in series with resonant circuit 85, 86 and condenser 87, which has one terminal connected to ground at the shield conductor 50. The input circuit of tube 26 in amplifier 20 includes its control electrode and cathode and this circuit is coupled to the resonant circuit 85, 86 whereby amplified oscillations transmitted from control oscillator 10 through amplifier tube 77 are supplied to the input circuit of tube 26. This input circuit may be traced from the conlOE aha:

trolelectrode through resonant circuit 85, 86, lead 19' through switch 28' and either directly or via generator 27 to choke coil 30, resistances 71, 31, 31 and 29 in series to ground and thence to the cathode of tube 26 by way of the shield conductor 50, condensers 88 and the secondary winding of transformer 89. The space current circuit of tube 26 may be traced from its anode through high frequency choke coil 32 to the positive brush on the second armature of generator 79 through the armature to the negative brush 91, positive brush 78 of the first armature through leads 81, slip rings 82, coils 83 to ground andthence to the cathode of the tube by the path already traced. A high frequency output circuit for tube 26 is substantially the same as for the tube 26 of Fig. 1 and will not again be traced. The feed-back circuit for this tube also includes the condenser 42 for obtaining feed-back control. In this circuit, resistances 44, 44 and 44" are enclosed in a separate shielding compartment 92.

The input circuit of tube 43 is connected to its control electrode and may be traced through the high frequency choke coil 46, resistances 31, 31 and 29 to ground and thence by way of condensers 93 and the secondary winding of transformer 94 to the cathode of the tube. The space current circuit of tube 43 is connected to its anode and is traced from this point through high frequency choke coil 51 to the neutral point of the star connected secondary winding of three-phase transformer 95, from the respective outer terminals of this transformer winding to the mid-tap on the secondary windings of delta-connected, three-phase transformers 96, to the cathodes of space discharge rectifiers 97, to ground and thence to the cathode of tube 43.

The high frequency output circuit of tube 43 is identical with that shown in connection with tube 43 of Fig. 1 and will not be again described. The antenna 65 is connected to ground through the inductance 64 and condenser 63.

The filament current for tub-es 26, 43 and 77 is supplied by the three-phase transformers 7 6, 89 and 94, delta-connected to an alternating current generator 102. The rectifiers 97 have their filaments heated by current from transformers 96 which are also delta connected to generator 102. The current to be rectified is supplied through transformer which has its primary delta-connected to the generator 102 and its secondary star con nected to the rectifiers.

The key 103 is arranged to provide a low impedance path in shunt to resistance 31 thereby reducing the blocking potential applied to the control grid of tube'26 so that this tube generates oscillations when driven by the oscillations supplied by the oscillator 10 through the tube 7 7 and its associated circuit. These oscillations are applied to the input circuit of the tube 43 Which is thereby caused togenerate oscillations.

The modulated continuous wave method of signaling or the continuous wave method may be employed in the manner described in connection with Fig. 1. Generator 2'? is arranged to supply low frequency modulating waves to the input circuit of the tube 26 as described in connection with the circuit of Fig. 1. x

The connection of leads 81 to the armature of generator 79 and the star connected coils 83 are provided to enable a divided potential to be obtained from this armature suitable for the space current source of tube 77 and for the polarized potential upon the control electrode of tube 43. This feature is the invention of H. M. Stoller and is claimed in his application Serial No. 229,450, filed October 28, 1927. The resistances 31, 31 and 29 are supplied by current continuously by the connection to the negative brush of the armature 1 of generator 79.

The condensers 42 and 105 associated with tubes 26 and 43 respectively, are provided to compensate to a certain degree for the inherent capacity between the anode and control electrode of each tube. By adjusting these condensers, the amount of energy fedback may be controlled, so that the circuits may be adjusted to the desired point on the verge of instability. Resonantcircuits 18, 22; 85, 86; 38, 40; and 57, 58 are all tuned to the same frequency at which all the amplifiers are designed to oscillate.

The piezo controlled oscillator 10 determines the frequency of the oscillations generated, in all of the tubes of the system, in the same manner as described in connection with Fig. 1. 7

What is claimed is:

1. In combination, a plurality of space discharge tubes having respective anodes,

cathodes and control electrodes, a resonantcircuit including an inductance, a connec tion from an anode of one tube to one termi-.'

nal of said inductance, a connection from a control electrode of another tube to the other terminalof said inductance, a connection from the control electrode of said first mentioned tube to an intermediate point of said inductance, and means including an adjustable condenser in said last mentioned connection for producing a feed back of energy between electrodes of atleast one of said tubes for causing regeneration.

2. In combination, a tandem system of space discharge tubes, each tube having three electrodes, a resonant circuit connected to unlike electrodes of at least two different tubes and also connected to unlike electrodes of the same tube, a source of constant frequency waves connected to electrodes of'one of said tubes, and means having reactance of the order of that between electrodes of said tubes connected to the respective control electrodes for adjusting said system to the verge of instability.

3. In an amplifier, a plurality of space discharge tubes having electrodes including anodes and control electrodes, a source of constant frequency waves coupled to a first tube and a load circuit coupled to a second tube, a path, resonant to the frequency of said source, connected to the anode of the first tube and the control electrode of the second tube, and a path between the anode of the first tube and the anode of the second tube, said path including a variable reactance.

4. In a radio transmission system, an an tenna, a high power amplifier adjusted to the verge of instability and coupled to said antenna, an amplifier of smaller power adjusted to the verge of instability and coupled to said first amplifier, and a piezo-crystal controlled amplifier adjusted to generate continuous constant frequency oscillations, coupled to said small power amplifier, and means adapted to cause the oscillations, from said last named amplifier, to start self-oscillation in said power amplifiers.

5. In a radio transmitting system, an antenna, a high power space discharge tube coupled to said antenna, a space discharge tube of lower power coupled to said first tube, said high and low power tubes being included. in circuits adjusted to the verge of instability, a piezo crystal controlled oscillator of lower power than said low power tube coupled to said low power tube and adapted to cause the generation of oscillations of very large power in both the associated circuits at a substantially constant frequency.

6. In a signal transmitting system, a low power oscillator, a medium power amplifier and a high power amplifier coupled in tandem to said oscillator, said amplifiers, being coupled in tandem in the order of their power capacities, and having coupled input and output circuits adapted to generate oscillations of constant frequency only when said oscillator tube is generating oscillations.

7. In a radio transmitting system, a plurality of space discharge amplifiers in tandem each of said amplifiers being designed to generate oscillations, an antenna, and means for coupling said tandem amplifiers to said antenna comprising a low pass filter having a capacity reactance for desired waves and a high impedance for harmonic waves.

8. In a signal transmission system an electron tube oscillator. an electron tube amplification system having its input circuit connected to the output circuit of said oscillator and a high potential source for impressing a positive potential upon the output circuit of said oscillator and a negative potential upon the input circuit ofsaid power amplifier.

,sseesv 9. In a signal transmission system a plurality of electron tubes each having grid, filament and plate electrodes, input and output circuits interconnecting said electrodes, one of said electron tubes being arranged for the production of high frequency oscillations, another of said electron tubes being arranged for the amplification of the oscillations thus produced and a high potential source interposed between the output circuit of said first mentioned electron tube and the input circuit of said second mentioned electron tube for impressing a positive potential upon the plate electrode of said oscillator and impressing negative potential upon the grid electrode of said power amplifier.

10. In a signal transmission system a plurality of electron tubes each having grid, filament and plate electrodes, input and output circuits interconnecting said electrodes, one of said electron tubes functioning for the production of high frequency oscillations and the other of said electon tubes functioning as power amplifier, apiezo electric crystal connected in the input circuit of said first mentioned electron tube for sustaining oscillations in said circuits at a frequency corresponding to the frequency of said piezo electric crystal element, and a source of potential havin value required for operation with said piezo electric crystal element, said source of potential having its positive terminal connected with the plate electrode of said first mentioned tube and having its negative terminal connected with the grid electrode of said second mentioned tube.

11. In a high frequency signal transmission system a combination of a plurality of electron tubes, each of said tubes having grid,

filament and plate electrodes, input and out- 7 put circuits interconnecting said electrodes, at least one of said tubes functioning as an oscillator and another of said tubes functioning as a power amplifier, means coupling the output of said oscillator with the input of said power amplifier and a circuit interposed between the plate electrode of said oscillator and the grid electrode of said power amplifier, said circuit including a source of potential with choke coils on opposite sides thereof, the negative terminal of said source connecting with the grid electrode of said power amplifier and the positive terminal of said source connecting with the plate electrode of said oscillator.

In witness whereof, I hereunto subscribe my name this 27 day of June A. 1)., 1925. GUSTAVE CHARLES on COUTOULY. 

